Self-propelled row-crop field sprayers are specialized agricultural machinery for applying liquids, such as fertilizers or insecticides, to crops planted and grown in multiple parallel rows. Adjacent pairs of rows are tightly spaced for maximizing the plant density of the row crop being grown. As a result, row-crop field sprayer tires have a narrow section width and a high aspect ratio so that the tire can travel within the intra-row space. Because row-crop field sprayers are extremely massive agricultural-machines, their pneumatic tires must have the ability to carry large loads. Pneumatic tires for the row-crop field sprayer also have to have a large rim diameter so that the field sprayer can clear the plants in the crop rows. Moreover, the pneumatic tires must exhibit good traction in either wet or dry conditions. In addition, row-crop field sprayer tires must be designed to withstand hard surface roading as the row-crop field sprayer is moved on paved roads between fields at a transport speed significantly faster than the service speed in the field.
As the spacing between adjacent rows has narrowed for increasing the crop density, a need has arisen for narrowed pneumatic tires for row-crop field sprayer service. Because the tire load increases as the footprint narrows, conventional agricultural pneumatic tires cannot satisfy the full range of performance and design parameters required for row-crop field sprayer service. In particular, the lugs of such conventional agricultural pneumatic tires experience adverse consequences, such as cracking, tearing or, at the least, irregular wear patterns, resulting from hard surface roading.
The inferior performance of conventional agricultural pneumatic tires arises from the faceted leading edge of the lugs, which define outside corners that provide stress concentration points under the conditions of high loading and fast speed. The leading edge experiences a significantly larger strain than the lug's trailing edge so that the outside corners on the leading edge experience significant strains. In particular, tires having conventional lug widths are prone to deflection which creates cracking, tearing and irregular wear patterns. An improved tread with unique lug profiles has been described in related and co-pending application publication US 2004/0118497 which is incorporated herein by reference in its entirety.
In addition to the problems associated with the tread a second issue is the focus of this invention which is directed to the structural strength of the carcass. Under severe and somewhat extreme tire durability testing the tire as described in US 2004/0118497 exhibited carcass turnup separations at maximum loads at inflation in as few as 400 hours of service. These turnup separations eventually can cause the sidewalls to crack and cause a loss of inflation. Therefore, conventional agricultural pneumatic tires for service with row-crop field sprayers are particularly susceptible to the aforementioned adverse consequences, which significantly reduce tire durability.
For these and other reasons, it would be desirable to provide a pneumatic agricultural tire for row-crop field sprayer services that can provide superior load carrying capacity wet and dry traction, that can carry heavy loads on a narrow-width ground-contacting footprint, and that does not experience any significant adverse consequences due from hard surface roading.